1. Field of the Invention
The present invention relates to signal processing, and, in particular, to error-correction encoding and decoding techniques such as low-density parity-check (LDPC) encoding and decoding.
2. Description of the Related Art
In communicating a data signal from a transmitter to a receiver, noise may be introduced into the signal causing the signal to be distorted upon arrival at the receiver. As a result of this distortion, the receiver might not correctly recover the transmitted information. In such cases, the transmitted signal may need to be retransmitted so that the receiver may have another opportunity to recover the transmitted information. However, resending the transmitted signal increases the amount of time that it takes to provide the transmitted information to the user. To reduce the frequency of retransmissions, and therefore reduce the amount of time that it takes for the transmitted information to be delivered to the user, the transmitter may encode the transmitted signal using a channel-coding scheme. A channel-coding scheme adds redundant or additional data to the signal to be transmitted. The receiver then uses this redundant or additional data to detect and/or correct errors. If the channel-coding scheme is effective, then the transmitted data may be recovered correctly without the need to retransmit the data.
One particular channel-coding scheme that has received attention in recent years is low-density parity-check (LDPC) coding. LDPC codes, which are typically defined using parity-check matrices, provide excellent performance that comes relatively close to the Shannon limit. A discussion of LDPC codes and LDPC decoding is presented in Hocevar, “A Reduced Complexity Decoder Architecture via Layered Decoding of LDPC Codes,” Signal Processing Systems, IEEE Workshop on Signal Processing Systems Design and Implementation, pgs 107-112, October 2004, the teachings all of which are incorporated herein by reference in their entirety.